Thermal processing torches, such as plasma arc torches, are widely used in the heating, cutting, gouging and marking of materials. A plasma arc torch generally includes an electrode, a nozzle having a central exit orifice mounted within a torch body, electrical connections, passages for cooling, and passages for arc control fluids (e.g., plasma gas). Optionally, a swirl ring is employed to control fluid flow patterns in the plasma chamber formed between the electrode and the nozzle. In some torches, a retaining cap can be used to maintain the nozzle and/or swirl ring in the plasma arc torch. In operation, the torch produces a plasma arc, which is a constricted jet of an ionized gas with high temperature and sufficient momentum to assist with removal of molten metal.
The operation of a plasma arc torch can be powered, at least partially, by a battery pack including one or more battery cells. However, such a design poses a challenging technical problem due the nature of batteries. For example, battery performance is often reduced in cold-temperature environment. Hence, an increased number of battery cells are often required to maintain a minimum input voltage supplied to the plasma arc torch, thereby increasing the overall size, weight and cost of the battery pack. In today's market, no light-weight, reasonably-sized and low-cost battery packs exist that can power a plasma arc torch to enable relatively long cutting time at a wide range of environmental temperatures. In addition, a plasma arc torch system needs to maintain many other battery attributes within acceptable operating ranges so as to optimize battery performance while minimizing battery cost, size and weight. These battery attributes include, for example, battery voltage, current, number of charge and/or discharge cycles.